District Heating in Reykjavik and Electrical Production Using Geothermal Energy
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GEOTHERMAL TRAINING PROGRAMME IGC2003 - Short Course Orkustofnun, Grensásvegur 9, September 2003 IS-108 Reykjavík, Iceland Reykjavik energy - District heating in Reykjavik and electrical production using geothermal energy Einar Gunnlaugsson Orkuveita Reykjavikur, Bæjarháls 1, IS-110 Reykjavik, Iceland Abstract Geothermal water has been used for over 70 years in Reykjavik for heating of houses. Orkuveita Reykjavikur operates the largest municipal district heating service in the world. It started on a small scale in 1930 and now it serves more than half of the nation's population. The harnessed power of the geothermal areas is about 700 MW thermal. Annually, 60 million cubic meters of hot water flow through the Utility's distribution system. From 1998, electricity has been co-generated from geothermal steam along with hot water for heating. 1 Introduction Geothermal water has been used for centuries for heating houses. The oldest geothermal district heating system in the world is most likely in the town Chaides-Aigues in Massif Central in France. The town is located in a narrow valley about 750 – 800 m a.s.l. Old manuscripts show that 82°C geothermal water was used to heat houses in the town in the 14th century. The oldest geothermal heating system in the United States began delivering water in 1892. This was in Boise, Idaho where 77°C water from drillholes was used to heat houses along the avenue, which led to the hot spring area. In 1998, the geothermal water was still being used to heat 226 homes and 36 commercial buildings in downtown Boise. In Iceland, drilling for hot water started in 1928 at the thermal springs in Reykjavik. Fourteen drillholes were drilled and the result was 14 l/s of about 87°C water. In 1930, a 3 km long pipeline was built, and the first house connected. This was the beginning of geothermal district heating in Reykjavik. Shortly thereafter, a hospital, another schoolhouse, an indoor swimming pool and about 70 private houses were connected to the district heating. This is now the largest geothermal district heating service in the world. About 87% of all houses in Iceland are heated with geothermal water. Almost 90% of the country’s inhabitants are connected to a district heating service that make use of geothermal heat. In Iceland, there are 29 district heating services, each serving an area ranging from one municipality to several adjoining municipalities. Figure 1 shows the water production for the 20 largest heating services in Iceland. Today, geothermal energy is used for district heating in at least 9 capitals of the world, i.e. in Addis Ababa (Ethiopia), Beijing (China), Budapest (Hungary), Bucharest (Romania), Paris (France), Reykjavik (Iceland), Rome (Italy), Sophia (Bulgaria) and Tbilisi (Georgia). 67 Gunnlaugsson 68 IGC2003 – Short Course Water production in 1000 m3 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 Reykjavík Suðurnes Akureyri Hveragerði Selfoss Skagafjörður Akranes Borgarfjörður Mosfellsbær Seltjarnarnes Laugarás Húsavík Ólafsfjörður Dalvík-Árskógsströnd Flúðir Þorlákshöfn Egilsstaðir og Fell Rangæinga Blönduós Siglufjörður Húnaþing vestra Figure 1: Water production of the largest district heating services in Iceland. Data from Samorka-home page. 2 Reykjavik Energy Reykjavik Energy entered its first year of operations in 1999 following the merger of the city's Electric Power Works and District Heating Utility. On January 1st 2000, Reykjavik Water Works merged with Reykjavik Energy. All these companies were leading players in the Icelandic energy sector, and merged to create a dynamic new company to handle procurement, sale and distribution of electricity, cold water and geothermal hot water for space heating. The year 2001 was especially eventful for Reykjavik Energy. First the distribution systems were greatly enlarged when Reykjavik Energy took over Thorlákshöfn Heating Utility; preparations for a hot water distribution system were started in Grímsnes and Grafningur parish; and last, but not least, a contract was completed for the mergers of Akranes Utilities and the Borgarnes Heating Utility with Reykjavik Energy. Reykjavik Energy operates the world's largest and most sophisticated geothermal district- heating system - an electricity distribution network and a water distribution system that meets the most demanding international standards for the quality of water and its environment. The area serviced by Reykjavik Energy reaches from Kjalarnes northwest of the capital and all the way south to Hafnarfjordur, an area where more than half the nation's population lives. IGC2003 – Short Course 69 Gunnlaugsson District heating in Reykjavik started on a small scale in 1930. In 1933, about 3% of Reykjavik's population were connected to Reykjavik District Heating. At that time, coal was mainly used for heating, and dark clouds of smoke were commonly seen over Reykjavik. Moreover, pipelines were laid to nearby municipalities, which are now supplied with geothermal water by the district heating in Reykjavik. The use of geothermal water in Reykjavik for space heating instead of fossil fuels reduces air pollution. Today, almost all houses in the area are connected to the district heating system. The district heating in Reykjavik serves 57% of the population of Iceland with geothermal water, and is the world’s largest municipal geothermal heating service. The installed power is about 750 MW. 3 The low-temperature fields Three low-temperature geothermal areas are utilized for district heating in Reykjavik. In the low-temperature fields, there are a total of 52 exploitation wells with a total capacity of about 2300 l/s (Table 1). Table 1: Summary of the geothermal fields Field Temp Capacity No. of exploitation °C l/s wells Laugarnes 125-130 330 10 Elliðaár 85-95 220 8 Mosfellssveit 85-95 1700 34 The exploitation of geothermal water from the Laugarnes field began in 1928-1930 with the drilling of 14 shallow wells near the Þvottalaugar thermal springs. The deepest well was 246 m deep and the well field delivered 14 l/s of artesian water at a temperature of 87°C. This water was used for heating schoolhouses, a hospital, swimming pools, and about 70 residential houses. In 1958, further drilling in the Laugarnes area commenced with a new type of rotary drilling rig, which was able to drill deeper and wider wells than previously possible. Deep well pumps pumped the water from the wells, whereas the water previously extracted in the area had been free artesian flow from the wells. The yield increased to 330 l/s of 125 to 130°C water. Now there are 10 production wells in the field, which cover about 0.28 km2 and located at a junction of a caldera and a fault-scarp. The temperature is 110 to 125°C at 400 to 500 m depths and increases with depth. The highest measured temperature is 163°C at 2,700 m depth. The main aquifers are at 1,000 to 2,000 m depth. The Elliðaár field had minor surface manifestations before drilling with a maximum temperature of 25°C. Drilling began in the area in 1967, finding aquifers with 85-110°C. The exploitation area covers 0.08 km2, but the manifestations cover 8 – 10 km2. Prior to drilling in the Reykir area, the artesian flow of thermal springs was estimated to be about 120 l/s of 70-83°C water. After drilling, the water from this area was piped to Reykjavik and by the end of 1943 about 200 l/s of 86°C water was available for heating houses in Reykjavik. After 1970, the deep rotary drilling of large diameter wells and installation of pumps redeveloped the Reykir field. The yield from these wells then increased to 2000 l/s of 85-100°C water. Gunnlaugsson 70 IGC2003 – Short Course The Mosfellssveit geothermal field, which is about 5.5 km2, is geographically divided into sub-areas, Reykir and Reykjahlíð. It is located between two calderas and the stratigraphy consists of lavas and hyaloclastite layers cut by numerous faults and fractures. Altogether, 34 exploitation wells are in the field. The temperature is in the range of 65 – 100°C. In general, there are more dissolved solids in geothermal water than in cold water - sometimes so much that it is not considered healthy for consumption. The low-temperature geothermal areas utilized for district heating in Reykjavik are low in total dissolved solids (Table 2) and can be used directly for heating and even cooking and drinking. This water al- most fulfills the requirements of drinking water codes. The sulphide concentration is higher than allowed in drinking water as well as the pH value. The geothermal water from the wells in Reykjavik and in Mosfellssveit comprise about two-thirds of the hot water in the distribution system. One-third comes from Nesjavellir. 4 The Hengill geothermal area The Hengill area east of Reykjavik is one of the largest high-temperature areas in Iceland. The geothermal activity is connected with three volcanic systems. The geothermal heat in Reykjadalur and Hveragerði belong to the oldest system, called the Grensdalur system. North of this is a volcanic system named after Hrómundartindur, which last erupted about 10,000 years ago. The geothermal heat in Öldukelsháls is connected with this volcanic site. West of these volcanic systems lies the Hengill system, with volcanic fractures and faults stretching from the southwest through Innstidalur, Kolviðarhóll and Hveradalur (Hot Spring Valley) and to the northeast through Nesjavellir and Lake Þingvallavatn. Several potential geothermal fields are found within the Hengill complex. Only two of these areas have been developed - one for space heating, industrial use and greenhouse farming in the town of Hveragerdi; and at Nesjavellir, where Orkuveita Reykjavikur operates a geothermal power plant producing 90 MWe of electricity and about 200 MWt of hot water for space heating.